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400D - Out-of-focus when replaced focuseing screen

Started Mar 2, 2021 | Questions
Poppasteve New Member • Posts: 1
400D - Out-of-focus when replaced focuseing screen

Hi there,

I have an old Canon 400D I'm shooting with. I mostly use it with some older Olympus OM Zuiko manual lenses (using a cheap OM-EFS adapter), so i recently replaced the original focusing screen with a split-image one but, unfortunately it fails to focus correctly.

Firstly I thought it was an adapter /lens issue but I get the same results with the kit lens (Canon 18-55). With this lens, when the camera beeps for focus, the image in the view finder is split, but the saved photo is fine-focused.

The focus is of by some factor, and I'd like to know if there's a way to compensate for this.

I'm sending a photo to help you understand my problem.

Thank you in advance.

ANSWER:
This question has not been answered yet.
Canon EOS 400D (EOS Digital Rebel XTi / EOS Kiss Digital X)
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guinness2
guinness2 Veteran Member • Posts: 4,617
Re: 400D - Out-of-focus when replaced focuseing screen

A focusing screen which fails to focus is, well, faulty. Try to fit it better or send it back home, if there is not an  exact fitting guide for it on that particular camera.

Good luck.

 guinness2's gear list:guinness2's gear list
Canon EOS Rebel SL3
Ray UK Contributing Member • Posts: 977
Re: 400D - Out-of-focus when replaced focuseing screen

Often fitting a non OEM split image screen will require adjustment to the shims that are fitted under the original (between the screen and the prism). Try first by removing the original shim and see in which direction the error moves, then you will know if you need to add or subtract to this thickness. In the past I have used a couple of tiny strips of self adhesive aluminium foil tape of the type that is used on air conditioning pipes. The foil tape is preferable because it is about 0.02mm thick and doesn't expand or contract much with temperature changes. The whole process is much easier if you have a micrometer to measure the thickness of the original shim.

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